The present invention relates to a device for cutting a web of paper in a printer.
Cutters of the type to which the invention pertains include, for example, a cutting bar having a right angle type cutting edge and being disposed on the transport path of the paper. The cutter may, in addition, include a cutting roll which rolls along the cutting edge. Other types of cutters are based on tearing along a line of perforations or the like or by employment of the shearing principle. Cutters of the latter types have been used for example in ticket printers in which the individual tickets are cut from a roll. A similar situation arises from the printout of account statements or the like. The cutting proper is carried out in these systems, for example by means of impact or rotating cutting blades or through a blade which moves on a carriage. Basically, all these cutting devices operate by shearing, whereby any part in the web being subjected to shearing is located in the intersection of two edges moving relative to each other. If one uses a device that tears along a perforation line the roll of paper has to be provided with such perforations prior to any cutting or tearing. Tearing without pre-perforating is practiced in so called shredders, using interdigitized rolls having stepwise differing larger and smaller dimensions. As the rolls wear, the cutting line deteriorates in quality which, considering the purpose of the device is an unimportant aspect.
A more specific problem can be defined as follows. In certain cases (printers), plural webs run next to each other, and just one is to be cut without cutting the others. If one intends to use impact cutters or rotating cutting blades, one needs one cutting blade per web or sheet. If the webs differ in width or if the same printer is to be used for printing on differently wide webs at different times, one has to exchange the blades accordingly. If one uses a cutter with a moving carriage for the blade, one will always have to cut all of the webs being located between the particular one to be cut and the left-hand or right-hand starting position of the cutter carriage. Alternatively, the webs which are not to be cut along the carriage travel path have to be retracted which complicates matters considerably.